In conjunction with oral healthcare, a primary principle of plaque removal with a toothbrush (e.g., a power toothbrush) is to get sufficient bristle tip pressure to the toothbrush head. Optimizing power transfer from the motor to the brush head is one mechanism for achieving this goal. Similar goals of maximizing power transfer efficiency are also desired with other types of personal care appliances.
Generally, a toothbrush head must be coupled to a toothbrush handle by a mechanism that both allows easy removal and replacement, while preventing the toothbrush head falling off while in use. However it must not be loose and as a result rattle and amplify vibrations that impact on the user experience. This involves compromises in design, in particular the clearance tolerances allowed between a drive shaft of the handle of the toothbrush, and the corresponding fitting of the toothbrush head. There must be sufficient clearance that the two parts are easily coupled and separated over all parts made, but if the tolerances are too large, then there will be rattling during use while the drive shaft is imparting drive forces to the brush head, enabling the cleaning action. This rattling can detract from the user experience of using the toothbrush.
FIG. 1 shows a cutaway side view of the lower interior portion of a conventional toothbrush head 2. The toothbrush head 2 has a body 3 with a coupling receptacle or cavity 4 that is shaped to receive a drive shaft of the handle. The conventional toothbrush head 2 is designed to fit on to the end of the drive shaft by means of a press fit.
Thus, in view of the above problems, improvements to personal care appliances and attachment structures for personal care appliances are desired.